Research

Department of Biochemistry

This page gives a brief overview of the research activities in the different laboratories. Further details will be available on the individual lab home pages as these are developed in future. New research pages will be announced here; this page will also contain links referencing them. So watch this space!

Natural products from Salsola tuberculatiformis

Salsola tuberculatiformis or “die bos”, which causes prolonged gestation and contraception, has a long history in this department. The research started with Prof KJ van der Merwe in the early 1970s and is still continuing. The problem has different facets:

  • Dr Ann Louw's group is presently investigating the effects of an analogue of the active compounds in the shrub on the synthesis of CBG and SHBG and on the glucocorticoid receptor.

  • Prof Pieter Swart's group is concentrating on effects on steroidogenesis: compounds that inhibited certain cytochrome P450-dependent steroid hydroxylases were isolated from Salsola. The structures of these labile substances were subsequently investigated and more stable analogues were synthesised. Parallel to the structure determination work the control and expression of mammalian adrenal steroidogenic cytochromes P450 were also investigated. This work was extended to include sheep, baboon and rock rabbit steroidogenesis. Several genes have since been cloned and expressed for the first time.

The Triple-J Group: Molecular cell physiology

Profs Jannie Hofmeyr, Jacky Snoep, and Johann Rohwer lead the Triple-J Group for Molecular Cell Physiology. Johann joined the group in 1997, after completing his PhD at the University of Amsterdam where he studied the interaction of functional units in metabolism, mainly using the bacterial phosphotransferase system as experimental subject. Jacky, previously an Assistant Professor at the Free University in Amsterdam, joined the group at the beginning of 2000 after taking up a new position in the department. The Triple-J Group studies the control and regulation of cellular processes using theory, computer modelling and experimental approaches. A main project is the development of a theoretical framework, based on control analysis, for describing metabolic regulation in an integrative cellular context that includes metabolism, signal transduction and the genetic hierarchy; aspects of this theory are studied experimentally in yeast and bacteria. Besides extensively using computer simulation for understanding cellular network behaviour and regulation, the group is also involved in the development of new modelling tools. More and more molecular biologists, in the broad sense of the term, are recognising the need for this type of integrative approach to understanding living systems.

New!  Simulate metabolism online at the Triple-J Web Simulation Project!

New!  Or download PySCeS (an open-source cellular systems simulation platform developed in our group) to do the modelling yourself!

Regulation of gene expression

Research in Prof Janet Hapgood's laboratory is focussed on basic molecular mechanisms of regulation of expression of genes involved in reproduction, using biochemical and molecular biological techniques. The role of natural steroids, as well as other potential nuclear ligands and their receptors, including a putative contraceptive agent, is being investigated by a combination of Northern blotting, RT-PCR, in vitro transcription/translation, protein-DNA binding assays, promoter functional assays in eukaryotic tissue culture cell lines and ligand-receptor binding assays. The team consists of 7 postgraduate students, a research assistant plus several collaborators, both from within the Department and at other universities in South Africa and overseas. Funding is obtained from FRD, MRC and Stellenbosch University.

Applied agricultural research

Research in Prof Dirk Bellstedt's lab is primarily directed at applied agricultural problems in South Africa. Maryke Appel (PhD student) is currently applying the differential display technique to analyse the resistance response of stone fruit trees to the Pseudomonas syringae pv syringae elicitor protein called harpin. This bacterial disease causes major losses in the deciduous fruit industry. Johann Strauss (M Sc student) is developing diagnostic methods (ELISA and PCR) for the detection of bean pathogenic bacteria which will be used to limit disease spread by infected seed beans. Annelise Blignaut (PhD student) is analysing ostrich immunity against Newcastle disease virus, which is the biggest limiting factor in ostrich meat exportation from this country. Johann Lombard (M Sc student) is analysing plant hormonal interactions during rest break of grape vines using plant hormone immunoassays. Dirk is also involved in plant phylogenetic work based on DNA sequencing on African orchids called disas and Alison van der Merwe (PhD Botany) is applying these techniques to some bulbous plants.

Antimicrobial peptides

Dr Marina Rautenbach's group investigates structure-function relationships of various antimicrobial peptides using synthetic analogues (click here for profile). In a world laden with bacteria, fungi and parasites, many strategies of defence have evolved among the living organisms in the fight for survival. One of the weapons in this repertoire of host defence is a group of peptides with pronounced antimicrobial activity. For example, various antifungal peptides are produced by strains of Bacillus subtilis, one of which, iturin A, is being studied with the aid of synthetic iturin A analogues. Iturin A, a cyclic lipopeptide, is active against certain stone fruit pathogens, and also against some of the major postharvest pathogens in table grapes. In this project the influence of peptide length, cyclisation, hydrophobicity, interaction with alkali metal ions and chirality on activity of iturin A is investigated. In a second project, the functional synergism between a-helical antimicrobial peptides and conventional antibiotics is studied. A third project involves the investigation of the influence of immobilisation and peptide chain length on bioactivity of antimicrobial model a-helical peptides, selected from a combinatorial library. In a new project, atomic force microscopy (AFM) is used to investigate the mechanism of action and physical perturbation of target membranes by the a-helical antimicrobial peptides. In collaborative project with the Polymer Chemistry Unit, the self-assembly and antimicrobial activity of peptide bola-amphiphiles are investigated. Apart from various techniques to purify and measure bio-activity of the synthetic peptides in this laboratory, techniques such as electrospray ionisation mass spectrometry, circular dichroism, nuclear magnetic resonance spectrometry and high performance liquid chromatography are being utilised to characterise iturin A, bola-amphiphiles and the other antimicrobial peptides. This laboratory has both a peptide synthesis and amino acid analysis facility that also provide services to research collaborators and industry.